1. Field of the Invention
This invention relates to a control apparatus for a robot, and particularly to a control apparatus for a robot, which restrict an arm of the robot from exceeding a predetermined allowable working area.
2. Related Art
A multi-arm type industrial robot generally has plural arms (movable portions) jointed each other at plural joint portions. Each arm of the robot rotationally operates by receiving driving torque from a motor such as a servomotor as a driving unit via a transmission mechanism. A hand provided at a tip of the robot is operated as a result of combination of each arm operation in accordance with a program.
In such the industrial robot, particularly in the case where the tip of the robot is controlled by a linear interpolation so that the tip of the robot substantially linearly moves between two points, it is difficult at the time an operation program is developed to predict what locus each of the arms trances. Therefore, the arms may behave unexpected movements so that the arms may collide with peripheral equipment when the robot makes a test operation.
Therefore, the industrial robot generally restricts a working area in which each of the arms operates. In detail, a conventional industrial robot employs stoppers at limitation positions of the working area in which the arms are allowed to work (allowable working area) so that the arms do not exceed the stoppers. Furthermore, on an operation program viewpoint, a controller observes whether a position command value for the arm exceeds a normal working area, which exists within the allowable working area. When the controller detects that the position command value exceeds the normal working area, the controller applies brake to the arm to decelerate the arm with a predetermined deceleration so as to stop the arm.
However, in the conventional working area restriction system, the arm may collide the stopper without sufficiently deceleration if an interval between the stoppers and the normal working area is not enough.